Instrumentation for parallel magnetic resonance imaging
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Parallel magnetic resonance (MR) imaging may be used to increase either the throughput or the speed of the MR imaging experiment. As such, parallel imaging may be accomplished either through a "parallelization" of the MR experiment, or by the use of arrays of sensors. In parallelization, multiple MR scanners (or multiple sensors) are used to collect images from different samples simultaneously. This allows for an increase in the throughput, not the inherent speed, of the MR experiment. Parallel imaging with arrays of sensor coils, on the other hand, makes use of the spatial localization properties of the sensors in an imaging array to allow a reduction in the number of phase encodes required in acquiring an image. This reduced phase-encoding requirement permits an increase in the overall imaging speed by a factor up to the number of sensors in the imaging array. The focus of this dissertation has been the development of cost-effective instrumentation that would enable advances in the state of the art of parallel MR imaging. First, a low-cost desktop MR scanner was developed (< $13,000) for imaging small samples (2.54 cm fields-of view) at low magnetic field strengths (< 0.25 T). The performance of the prototype was verified through bench-top measurements and phantom imaging. The prototype transceiver has demonstrated an SNR (signal-to-noise ratio) comparable to that of a commercial MR system. This scanner could make parallelization of the MR experiment a practical reality, at least in the areas of small animal research and education. A 64-channel receiver for parallel MR imaging with arrays of sensors was also developed. The receiver prototype was characterized through both bench-top tests and phantom imaging. The parallel receiver is capable of simultaneous reception of up to sixty-four, 1 MHz bandwidth MR signals, at imaging frequencies from 63 to 200 MHz, with an SNR performance (on each channel) comparable to that of a single-channel commercial MR receiver. The prototype should enable investigation into the speed increases obtainable from imaging with large arrays of sensors and has already been used to develop a new parallel imaging technique known as single echo acquisition (SEA) imaging.
Brown, David Gerald (2005). Instrumentation for parallel magnetic resonance imaging. Doctoral dissertation, Texas A&M University. Texas A&M University. Available electronically from